SG_USA_April_2022

By Matthew Garcia, Ph.D., Beef Specialist, Utah State University PROJECT UPDATE Using Santa Gertrudis to Evaluate Heterosis in Intermountain West

W hen I was approached to write an update on the Santa Gertrudis Breeders International (SGBI) and Utah State University (USU) heterosis collaboration, I was somewhat surprised that this collaboration is now going into its fifth year! The original intent of this project was to reintroduce an evidence-based heterosis project to the industry as well as identify or dispel any concerns there may have been in using the Santa Gertrudis breed in a crossbreeding program. Since the project’s inception, we have seen dra- matic improvement in weaning weights, feedlot efficiency, and carcass quality

implant study in which cattle received no implant, one implant or two implants. Results of this study revealed there was no significant difference in gain between Santa Gertrudis and Angus that were implanted and no significant difference in non-implanted steers. Furthermore, there was almost an $80 economic incentive to implanting vs. not implant- ing Santa Gertrudis steers. A second study is currently being completed that looks at multiple implant effects on feedlot performance and carcass quality. Carcass Studies Another major objective of this study was to evaluate how Santa Gertrudis-

influenced steers would compare with respect to carcass quality and composition. We have collected carcass data from steers for two years and the results are promising. There was no discernable difference in marbling scores between Angus and Santa Gertrudis steers. However, Angus steers’ marbling scores seem to be more affected by implants than Santa Gertrudis steers, and Santa Gertrudis steers have averaged a 2.5 Yield Grade (YG) while Angus steers have an average YG of 3.2. We are currently feeding another group and expect additional data this summer. Disposition and Environmental Compatibility Evaluation One of the initial concerns with Utah producers dealt with incorporating Bos indicus genetics and the subsequent effects on temperament and the ability to deal with harsh northern Utah winters. When evaluating temperament, every trial that has been conducted has measured exit velocity out of the chute. Santa Gertrudis steers and Angus steers have shown no significant difference in exit velocity, and there have been no temperament issues noted by researchers or the farm crew. When evaluating environmental compatibility, there have been no issues calving or keeping calves alive when calving in February. Since the inception of the project, there have been six Santa Gertrudis calves lost during calv- ing season, but none was due to temperature acclimation. Cow Longevity and Performance While this part of the project is still in its infancy, female longevity was a major issue the project wanted to address. The premise was that by incorporating Santa Gertrudis genetics into the herd, we could potentially get more com- patible genetic predisposition in a forage-variable produc- tion environment and subsequent increased longevity due to the Brahman influence of the Santa Gertrudis breed. At the present time, USU is still in the building phase of our Santa Gertrudis female herd base. Currently, we have a group of F1 3-year-olds that are calving for the second time and a larger group of 2-year-olds that are calving for the first time. As we go forward, we will continue to incorporate replacement

and composition. In this article I will briefly describe some of the projects and results in which Santa Gertrudis are being utilized. Feedlot, Implant and Mineral Studies One of the original intents of this study was to evaluate how Santa Gertrudis-influenced cattle would perform in the feedlot. In year two, we found that Santa Gertrudis cattle were using 13 percent less feed to get to finish than their Angus-influenced counterparts. I’m happy to say we have finished two more groups of steers, and that number has remained the same. As a result of these feeding trials, it was decided that Santa Gertrudis would also be involved in an

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